1. Field of the Invention
The present invention relates to metal ceramic composites having excellent mechanical strength properties and a method for producing said composites.
2. Description of the Prior Art
Heretofore, metal ceramics composites having metal and a ceramics bonded through a metallizing layer, have been used for semiconductor integrated circuit parts, electronic circuit substrates or envelopes for electron tubes.
These metal ceramic composites are produced by carrying out metallizing processing on surfaces of a ceramic body, then effecting metal plating thereon and brazing the thus treated ceramic body with a metal body by using a brazing metal. Accordingly, between the metal body and the ceramic body of such a composite there is a bonding layer consisting of a metallizing layer, a metal plating layer and a brazing layer.
The bonding strength of the thus obtained metal ceramic composite is highly influenced by the properties of the metallizing layer which is an element for composing the bonding layer.
As compositions of the metallizing layer used for these metal ceramic composites, for example, those consisting of at least one metal of Mo, W, Mn, Fe, Ni, Co, etc. and at least one oxide of MnO, SiO.sub.2, Al.sub.2 O.sub.3, CaO, MgO, BeO, etc. have been well known and among them, a metallizing layer having a composition consisting of Mo metal, MnO, SiO.sub.2 and Al.sub.2 O.sub.3 has been broadly used as the metallizing layer by which a metal ceramic composite having high reliability can be obtained.
However, in prior metal ceramics composites, excellent gastightness is the most important requirement, so that as the metallizing layer to be used therefor, the layer having the similar coefficient of thermal expansion to the ceramics to be bonded is selected and the composition containing oxides showing a viscosity similar liquid at a relatively low firing temperature is preferable. Metal ceramics composites bonded through prior metallizing layers do not have high enough strength to be used as high strength mechanical parts.
Recently, an increasing the need for the application of ceramics to machine parts, has required the metal ceramic composites to have high bonding strengths between the metal and ceramic.